As an example of a resistance change memory, a phase change memory is a device that uses a property of transitioning between an amorphous state and a crystalline state by adding electrically generated heat to a chalcogenide material (Ge, Sb, Te), to perform storage. In a cell configured by a phase change memory, in a case of causing a phase change by Joule heat by an electrical current to carry out writing, when there is a transition from a low resistance state (set state, crystalline state) to a high resistance state (reset state, amorphous state), a large current is made to flow for a short time. Conversely, in a case of a transition from a high resistance state (reset state, amorphous state) to a low resistance state (set state, crystalline state), a relatively small current must be made to flow for a long time. In this regard, in a case of performing reading, a small current in comparison to a case of writing may be made to flow.
A semiconductor device provided with this type of phase change memory is disclosed in Patent Document 1. The semiconductor device is provided with a bit line selector wherein a line selected from a plurality of bit lines is connected to a bit line on a sense amplifier side, to precharge the bit line of the sense amplifier side to a desired level. Furthermore there is also provided a sense amplifier that amplifies and outputs a signal of a bit line on the sense amplifier side. This sense amplifier detects when potential of the bit line on the sense amplifier side, which has once been precharged, drops in accordance with a state (high resistance, low resistance) of a phase-change memory via the bit line, and determines data according to whether this potential is higher or lower than a reference level.
[Patent Document 1]
    JP Patent Kokai Publication No. JP2010-49792A